A polycarbonate resin is excellent in mechanical properties such as impact resistance, electrical properties, heat resistance, moldability, transparency, etc., and is widely used for various components for various display devices, interior components for automobiles or components for protective equipments.
In such applications, in a case where a lightweight transparent structural element is required, a sheet using a polycarbonate resin is commonly employed, and in such a case, it is frequently made into a multilayer sheet or subjected to additional treatment such as hard coat treatment.
Patent Document 1 discloses a single layer sheet of a polycarbonate resin having a 2,2-bis(4-hydroxy-3-methylphenyl)propane structure. This polycarbonate resin sheet has high surface hardness i.e. the surface hardness is 2H as pencil hardness, but the color of the sheet is poor and yellowish, and therefore, it is not useful for an application where the color is important. Further, the impact resistance is also poor.
Further, Patent Document 2 discloses a laminate sheet using, as a surface layer, a polycarbonate resin layer having a 2,2-bis(4-hydroxy-3-methylphenyl)propane structure and, as a core layer, a polycarbonate resin layer having a 2,2-bis(4-hydroxyphenyl)propane (i.e. bisphenol A) structure. In Patent Document 2, the polycarbonate resin of the bisphenol A structure has a pencil hardness of 2B and its surface is susceptible to scratching, and therefore, the surface hardness is improved by forming a laminate having a surface layer with high surface hardness provided on such a core layer. However, this laminate is poor in impact resistance, although its surface hardness is high.
Patent Document 3 discloses a polycarbonate resin laminate using, as a surface layer, a polycarbonate resin layer having a pencil hardness of at least HB and, as a core layer, a polycarbonate resin layer having a bisphenol A structure, and further having the surface layer covered with a hard coating. However, the impact resistance is inadequate, and besides, this laminate essentially requires the hard coating.
Further, Patent Document 4 discloses a sheet of a polycarbonate resin obtained by copolymerizing cyclododecane biscresol and bisphenol A, as a polycarbonate resin sheet having high surface hardness. Although the surface hardness is high, the impact resistance was inadequate.